1. Field of the Invention
The swinging piston heat machine belongs to the positive displacement heat machines, whose operation is grounded by variable working volumes, and which are applied as internal combustion engines (spark ignition, diesel), external combustion engines (steam engines, Stirling engines), and as compressors, pumps, and expanders.
2. Description of the Related Art
Free reciprocating piston internal combustion engines are known, whose stroke of piston (or pistons) is not limited by mechanical means and which could vary. These engines are designed to directly drive (with no motion conversion) oscillating electrical generators or other devices with periodical movement (compressors, piledrivers). The free-piston heat machines have some advantages in comparison to the machines with a fixed piston stroke, because variation of the piston stroke enables additionally to control duty of the machine. In the free-piston internal combustion engines it is possible to optimize the combustion process from the viewpoint of efficiency and minimized pollution. The absence of motion conversion, that is, realization of directly driving a secondary device, not only simplifies the structure of the primary device, but also decreases energy losses that are inevitable in any motion conversion.
Single-sided free-piston internal combustion engines having one cylinder are known. “Free-piston engine and method for the conversion of energy stored in fuel into electrical energy in a free-piston engine” (patent DE 04315046 A1, 10 Nov. 1994). A motion conversion is not used in this device, but a spring for reversing the piston is used. The spring complicates the structure of the device and decreases its reliability. In addition, the mechanical system of the engine with one cylinder is unbalanced, which promotes large vibrations of the frame. A similar device of the free-piston engine driving an oscillating electrical generator is also presented as one variant in the patent of French Republic N. 1309350, 8 Oct. 1962 “Dispositif electromagnetique de transformation d'energie”.
Doubled free-piston internal combustion engines are known. The pistons move in opposite directions decreasing frame vibration. U.S. Pat. No. 4,154,200 A, 15 May 1979 “Non-polluting heat machine with internal combustion”. Motion conversion is absent in this engine, but other imperfections remain, such as the necessity of springs to reverse the pistons of the single-sided engine.
The free-piston internal combustion engine is known, having two double-sided cylinders operating in opposite directions, and driving an oscillating electrical generator. Such engines can be springless. See corresponding variants of the patent of French Republic N. 1309350, 08 Oct. 1962 “Dispositif electromagnetique de transrofmation d′energie”. In addition, the doubled variant of such double-sided engines is provided too, in which vibration of the frame is eliminated. Consequently, such free-piston heat machines have the most advantages.
However, in all free-piston engines with linear motion pistons, large friction losses between the piston (or piston rings) and cylinder wall, or in other linear guides are inevitable. Moreover, the four-stroke operation of such engines is well nigh impossible, while the two-stroke operation is imperfect from the viewpoint of the utilization of the fuel and the quality of the combustion process.
The friction of the pistons or their guides can be radically decreased in the swinging (rotating) pistons heat machines.
In the swinging pistons internal combustion engine (patent DE 03303509 A1, 9 Aug. 1984 “Machines with double-acting pistons”), the piston assembly with two vanes of rectangular cross-section, which are symmetrically attached to the cylindrical hub, pivot around the axis of the cylindrical cavity. Four working chambers of the machines are formed between the two fixed vanes and two swinging vanes. The four-stroke and two-stroke operations of the engine are provided. In the later case, a usage of the inlet and exhaust ports in the housing, which are opened by the piston itself, is provided (instead of the valves). Other four-stroke internal combustion engines of analogous structure are also known. (U.S. Pat. No. 5,086,732 A, 11 Feb. 1992 “Four stroke concentric oscillating rotary vane internal combustion engine”). Both these engines have an advantage compared to the engines of linear pistons, that the rotating bearings are used as guides of the swinging pistons without friction from the pistons to the engine cylinder. The friction losses of the rotating bearings are markedly decreased due to the lesser mutual speed of the sliding surfaces. These engines have a compact and workable structure, because the housing cavity and swinging pistons are formed by planar and cylindrical surfaces. However, these engines have imperfections: motion conversion is applied, which converts the oscillation of the pistons into continuous rotation, and which ipso facto are mechanically fixing the pistons stroke; the mechanical system is unbalanced, and promotes vibration of the frame; the concrete strokes of the four-stroke operation of the engine occur in the asymmetrically displaced working chambers, which causes additional loads on the bearings and additional vibration of the device.
Also known are engines with two analogous coaxial assemblies of pistons, in which the piston assemblies are formed by two vanes of rectangular cross-section, which are symmetrically attached to the cylindrical hubs, and the piston's vanes move in the ring shaped cavity of rectangular cross-section forming four working chambers of variable volume (See patents: U.S. Pat. No. 385,856 A, 7 Jan. 1975, “Reciprocating rotary engine”; DE 04014279 A1, 23 Jan. 1992, “Four-stroke, rotary vane IC engine—has vane rotating in one direction only in circular, radial working chamber”; GB 02262569 A, 23 Jun. 1993, “Oscillatory rotating engine”; U.S. Pat. No. 5,537,973 A, 23 Jul. 1996, “Rotary engine with glow ignition system”). In all these devices the above-mentioned advantages of the rotary (or swinging) pistons engines are realized, that is, the small friction in the rotary guides, the compactness of the working chambers, and the workable structure. Consequently, from this standpoint, the mentioned analogues are the most similar to the invention. However, these analogues have imperfections. In all cases, motion conversion is used that employs the unidirectional rotation of the piston assemblies with periodically variable velocities, in this way achieving periodical variation of the working chambers; any external devices (engine's load) are also connected through motion conversion, that is, using the unidirectional rotation of the shaft; the variable velocities of the piston assemblies promote vibrations of the frame; and the four-stroke engine operation is realized in four working chambers, but in any instance the combustion occurs only in one working chamber, and therefore, the high-pressure zone is asymmetrical to the axis, which causes additional vibration and load on the bearings.